1. Field of the Invention
This invention relates to one-piece, stamped sheet metal, push-on stud retainers and in particular relates to relatively thin walled, one-piece, stamped sheet metal push-on stud retainers having minimal transverse dimensions and utilizing the relatively smooth continuous edge of a punched or pierced hole as the stud retaining edge of the stud retaining aperture.
2. Description of the Prior Art
One-piece, stamped sheet metal, thin walled stud retaining fasteners of the push-on type are well known in the prior art. Examples of such prior art devices may be seen by reference to U.S. Pat. Nos. 2,975,667, issued Mar. 21, 1961; 2,986,060, issued May 30, 1961; 3,032,807, issued May 8, 1962; and 3,108,371, issued Nov. 29, 1963. Many of the prior art devices were formed by punching or piercing an aperture into a sheet metal blank and then slotting or slitting the edges of the punched aperture to provide a stud retaining aperture having a plurality of stud retaining fingers. Other prior art devices were formed by punching or piercing a hole into a sheet metal blank from a first direction and then forming a generally dome shaped impression from the other direction to achieve a fastener having a generally frusto-conical cross-sectional shape. The forming of the generally dome shaped impression from the direction opposite the direction of the punching of the hole assured that the "burr edge" of the punched hole was the stud retaining edge of the stud retaining aperture. The above mentioned U.S. Pat. No. 3,108,371, at Column 4, lines 37 to 51, is an example of such a so-called "reverse formed" stud retaining fastener. Other prior art devices utilized a swaging operation to assure that the stud retaining edge of the stud retaining aperture was given a rough, biting surface. The prior art stud retaining fasteners operated by frictionally gripping the exterior side walls of a retained stud. Such prior art devices usually resisted attempts to remove the stud by bitingly penetrating the outer edge of said studs. While such prior art stud retaining fasteners were generally suitable for most applications, the present tendency to use such fasteners in so-called miniature and/or microminiature devices has led to an attempt to minimize the outer transverse dimensions of said fasteners. Reduction of the transverse dimension of such fasteners will allow the retention of studs on closer centerlines. Such attempts to minimize the other transverse dimensions have been relatively unsuccessful as the prior art push-on fasteners have utilized a stud retaining aperture having a rough biting edge or burred edge and/or a slotted or slitted edge to provide the stud engaging edge of such fasteners. The use of such burred edge and/or slitted edge has prevented attempts to minimize the outer dimensions of said prior art fasteners as the burred and/or slitted edges contained many cracks, discontinuations and/or irregularities therein which has resulted in cracking and/or other failure of the fastener body unless at least a predetermined minimal outer dimension thereof was provided.